This invention relates generally to methods for manufacturing electromagnetic relays such as the polarized type which comprising an electromagnet block and an electric switching block and, more particularly, to improvements in methods for manufacturing specifically the electric switching block of such electromagnetic relays.
In conventional electromagnetic relays of the kind referred to respective terminals of a plurality of switch sections each include a pair of normally-opened (NO) and normally-closed (NC) side fixed contact terminals and a movable contact terminal as well as terminals for electromagnetic coil or coils. The terminals are integrally embedded in a base body of an insulative material by being molded, typically. The pair of fixed contacts as well as their terminals are deviated from each other so as not to oppose each other. Also provided are a pair or movable contacts on both surfaces of a movable contactor spring plate secured at a base end to a movable contact terminal. These movable contacts are also deviated from one another so as to be engageable with each of the deviated fixed contacts, respectively. This is because, if the fixed contacts are opposed to each other, an upper die normally required for molding the base body cannot be used since the both contacts which are generally opposing through a very small distance get in the way of downward stroke of the the upper die member of the molding die. The latter defines the upper surface of the base body. Further, the integral holding of the terminals with the molding made base body becomes practically impossible. However, when the fixed contact terminals are deviated as in the foregoing, the entire base body can be molded by using a pair of split side cores. On the other hand, there has been a problem in the above arrangement in that, as the movable contacts are disposed as deviated at positions mutually different in the distance from the base end of the movable contactor spring plate, the resiliency constant of the spring plate at each position of the NO and NC side movable contacts is caused to be different from each other consequently a non-uniformity will arise in the contacting pressure of the respective movable contacts with the fixed contacts, whereby uniform reliability of contacting performance on both of the NO and NC sides cannot be achieved and hence the switching performances of the entire relay are deteriorated.
In manufacturing such electromagnetic relay as above, further, the respective contact terminals specifically in the switching block have been prepared separately from each other or at least one of the fixed contact terminals of the deviated positions has been prepared separately from the other fixed contact terminal and the movable contact terminal. On the other hand, at least the latter two terminals could be prepared in a common single metal strip. Thus, the manufacturing steps would be rather complicated and certain positional errors could have been involved in the deviated relationship between the respective pairs of the NO side and NC side contacts, resulting in deteriorations in the switching performances. Even in the event when the pair of fixed contact terminals or at least their fixed contacts are disposed to oppose each other, as shown in FIGS. 1A and 1B, the fixed contact terminal 3' and movable contact terminal 7' are prepared jointly in a single metal strip S' together with a coil terminal 9'. However, the other fixed contact terminal 4' must be prepared separately from the strip S' since it has been practically impossible to provide in the same strip the latter terminal 4' which is to be disposed in the opposing relation with a predetermined space to the former fixed contact terminal 3'. Yet, so long as at least the terminals 3', 7' and 9' are formed in the strip S', the manufacture of the relay is adapted to an automatic line operation and, in order that the separately prepared terminal 4' is incorporated in such line operation of the strip S', the terminal 4' is formed substantially in a reverse Z-shape as seen in FIG. 1A and is bent at the intermediate position as seen in FIG. 1B. Thus, its one end can be parallelly opposed to an end of the terminal 3' through the predetermined space while the other end can be joined to the strip S' at a position on the strip between the both terminals 3' and 7'. In performing the line operation, further, a large number of sets respectively including the terminals 3', 7' and 9' are sequentially provided in the strip S' which is usually provided in a hoop and arranged to be a long rectangular shape. Thus respective two sets of the terminals will be parallelly opposed for manufacturing both two-position transfer (2T) type and four-position transfer (4T) type electromagnetic relays. Accordingly, the joining work of the separately prepared terminals 4' must be performed for the respective large number of sets with a great deal of care for avoiding any positional error in the opposing and spaced relationship between the fixed contacts, and the manufacturing is rendered much complicated in steps, resulting in higher costs.
The present invention has been suggested to remove such problems as in the foregoings of the conventional method for manufacturing the electromagnetic relays of the kind referred to.
A primary object of the present invention is, therefore, to provide a method for manufacturing specifically the electric switching block of the electromagnetic relay having fixed contact terminals mutually opposing their contact carrying parts, which can be performed easily and yet with a higher assembling precision.
A related object of the present invention is to provide the method of manufacturing the electric switching block of the electromagnetic relays which can be performed through simplified steps and suitable to be adapted to an automatic mass-production.